It has long been known in the agricultural arts that certain biological, i.e. microbial, inoculants can be used with certain specific crop species to facilitate the growth of crop plants of that species or to assist the crops of that species in resistance to particular pathogenic organisms. For example, it has long been a common practice to inoculate soybeans and other legumes at plantings with bacterial cultures of the genus Rhizobium, so that the resulting Rhizobium cultures will nodulate within the roots of the soybean or other legumes to form colonies which will fix nitrogen symbiotically for the plant as well as the bacteria.
It has also been known in the prior art that many fungi are often found in association with the roots of many plants. The type of association is poorly understood and there is no clear understanding or agreement among mycologists as to which of such associations are symbiotic and which may be more properly termed pathogenic. The association produced by a fungal on the roots of a plant is referred to as a mycorrhizal association. In a mycorrhizal association, the hyphae of the fungal colony become interwoven with the plant root and root hairs in a poorly understood interaction. Such interactions have generally not been used for any specific benefit except that,in some circumstances, mycorrhizal cultivation of a fungus with a plant can be used to produce the fungus for food purposes. For example, a method is described in U.S. Pat. No. 4,345,403 to generate plants which are mycorrhizated with symbiotic fungi for the purposes of generating fungi for consumption.
It has also been reported specifically that some specific fungi have some capability to be antagonists for plant pathogens. For example, it has been reported that the fungus Talaromyces flavus has a capacity to be an antagonist for the fungal pathogen Verticillium dahliae in the cultivation of egg plant. Marois, et al., "Biological Control of Verticillium Wilt of Egg Plant Solanum-Melonjena in the Field", Plant Diseases, 66:12, pages 1166-1168 (1982). The use of the T. flavus inoculation was also reported, in that article, to result in an increased yield of fruits from the plant. The yield increase is described in the antagonistic effect of T. flavus on the verticillium species, although even the mechanism by which this effect is accomplished is not at all characterized or understood. In U.S. Pat. No. 4,259,317 a preparation for the protection of emerging sugar beets against damping-off, which is caused by a parasitic fungus, is disclosed which includes the use of the fungus Pythium oligandrum which is used as an inoculant on the sugar beet seed to prevent damage to the plant by other fungal species.
It has also been recognized that the Trichoderma fungus may be beneficial to certain edible crops. In one report, Papavizas, "Survival of Trichoderma-Harzianum in Soil and in Pea Pisum-Sativum Cultivar Perfectid-Freezer and Bean Phaseolus-Vulgaris Cultivar Blue-Lake". Phytopathology, 72:1, pp. 121-125 (1982), it was reported that the fungus Trichoderma harzianum could be isolated from soil and cultivated with pea and bean seedlings in soil. No teaching is presently known for the use of any species of Trichoderma fungi as an inoculant for corn.